The present invention relates generally to prosthetic devices, and more particularly to multi-axis prosthetic ankle joints.
A prosthetic ankle is a component which connects a prosthetic foot with a prosthetic lower leg. For smooth walking, especially, across uneven ground, it is important for the ankle to be designed for a full range of foot motion with respect to the lower leg prosthesis. One embodiment of such an ankle is described in U.S. patent application Ser. No. 09/893,887, which is hereby incorporated by reference herein. Most prosthetic ankles currently on the market, however, do not provide optimally controlled multi-axis motion. Often the prosthetic ankle has such a low stiffness that it effectively reduces any functional capabilities of the attached prosthetic foot, resulting in a choppy, unnatural and uncomfortable gait. Some ankles require adjustments to the assembly in order to achieve the desired function.
A full range of motion may be accomplished by the use of multiple axes of rotation in the ankle joint. However, conventional prosthetic ankle joints that provide multi-axis motion tend to require extensive maintenance including the replacement of parts in order to function properly. This is because the conventional ankle joint designs require elastic members to slide in contact with either a rigid surface, which is typically metallic, or another elastic surface. This surface-to-surface sliding motion is the primary cause of material breakdown.
It is therefore an object of the present invention to provide a multi-axis prosthetic ankle joint which does not suffer from the shortcomings of the prior art.
One embodiment of a multi-axis prosthetic ankle joint of the present invention includes a bottom component adapted to be connected to a prosthetic foot, a lower leg connection component adapted to be connected to a prosthetic lower leg, an elastomeric material securely connecting the bottom component with the lower leg connection component, and a mechanical device suspended in the elastomeric material. In this embodiment, the mechanical device comprises a first rigid element connected to the bottom component but not to the lower leg connection component, and a second rigid element connected to the lower leg connection component but not to the bottom component. The first and second elements interlockingly float in the elastomeric material, and are not in direct contact with one another, so as to permit relative movement of the bottom component and the lower leg connection component by deformation of the elastomeric material.
In this particular embodiment of the present invention, the mechanical device comprises a generally U-shaped first part connected to the bottom component so as to define a first aperture, and a generally U-shaped second part connected to the lower leg connection component so as to define a second aperture. The first part floatingly extends through the second aperture, and the second part floatingly extends through the first aperture.
An alternate embodiment of a multi-axis prosthetic ankle of the present invention may also include a bottom, prosthetic foot connection component adapted to be connected to a prosthetic foot, a lower leg connection component adapted to be connected to a prosthetic lower leg, an elastomeric material securely connecting the prosthetic foot connection component with the lower leg connection component, and a mechanical device suspended in the elastomeric material. In this embodiment, the mechanical device comprises a first rigid element in the prosthetic foot connection component that is not connected to the lower leg connection component, and a second rigid element connected to the lower leg connection component but not to the prosthetic foot connection component. The position of the first and second elements is maintained by the elastomeric material. The first element may act as a stop for restricting the range of motion of the lower leg connection component, but otherwise the first and second elements are not in direct contact with one another. As such, relative movement of the prosthetic foot connection component and the lower leg connection component occurs through deformation of the elastomeric material.
In this particular embodiment of the present invention, the mechanical device comprises a cavity in the prosthetic foot connection component that is substantially defined by a plurality of vertically extending walls, and a generally hook-shaped projection extending from the lower leg connection component. The hook-shaped projection of the lower leg connection component floatingly resides within the cavity in the prosthetic foot connection component. Contact between a portion of the hook-shaped projection and a rigid wall of the prosthetic foot connection component can be utilized to restrict the range of motion of the lower leg connection component. Other points of contact between the lower leg connection component and the prosthetic foot connection component may be similarly utilized.
By terms such as “interlockingly float” and “floatingly resides” it is meant that the first and second elements are suspended in the elastomeric material in close relation to one another, but are retained in position by the intermediary elastomeric material, not by contact with one another. Since the deformation of the elastic material permits multi-axis relative movement of the bottom component and the lower leg connection component, including translational movement, the ankle joint of the invention can simulate natural ankle motion by providing plantar flexion, dorsi flexion, inversion, eversion, translation and internal/external rotational movement. Such motion is optimally controlled by the multi-axis deformation of the elastic material, without sacrificing the energy return of the prosthetic foot. Further, since the components of the mechanical device are bonded to, and encased by, the elastomeric material, the ankle has the ability to absorb and damp both rotational and linear impacts.
As force is applied to either of these ankles, the ankle 5 moves in rotation and translation with a fluid motion by deforming the elastomeric medium. According to a further feature of the invention, at least one mechanical stop may also be positioned on/in either of these multi-axis ankle embodiments to prevent the relative angular movement of the ankles from deforming the elastomeric material beyond the elastic limit thereof. Since the deformation of the elastomeric material in both multi-axis ankle embodiments is thus always kept within the elastic limit, any tendency toward breakdown of the elastomeric material is further reduced.
In another embodiment of a multi-axis prosthetic ankle of the present invention, the ankle may include a bottom, prosthetic foot connection component adapted to be connected to a prosthetic foot, a lower leg connection component adapted to be connected to a prosthetic lower leg, an elastomeric material residing between the prosthetic foot connection component and the lower leg connection component, and a mechanical connection suspended in the elastomeric material. In this embodiment, the prosthetic foot connection component and the lower leg connection component are mechanically coupled and are preferably substantially encased within the elastomeric material. A portion of the prosthetic foot connection component may act as a stop for restricting the range of motion of the lower leg connection component. Unlike the previously described exemplary embodiments, this multi-axis ankle embodiment does not rely solely on the elastomeric material to maintain the positional relationship between the prosthetic foot connection component and the lower leg connection component. Consequently, in this exemplary embodiment of the present invention, relative movement of the prosthetic foot connection component and the lower leg connection component occurs through deformation of the elastomeric material as well as through the mechanical connection.
In this particular embodiment of the present invention, the mechanical connection may comprise a pin that resides in an aperture passing through both an upwardly-extending portion of the prosthetic foot connection component and a downwardly-extending projection of the lower leg connection component. A bearing, such as a spherical bearing, may be located in the downwardly-extending projection of the lower leg connection component to receive the pin and enhance movement of the lower leg connection component. The upwardly-extending portion of the prosthetic foot connection component may comprise two legs, such that the downwardly-extending projection of the lower leg connection component may reside therebetween. A dorsi-flexion stop may be located in the prosthetic foot connection component so as to contact a portion of the downwardly-extending projection of the lower leg connection component and limit the range of motion thereof. Alternatively, a dorsi-flexion stop may be located in a projection of the lower leg connection component and adapted to contact a portion of the prosthetic foot connection component in order to limit ankle movement.
As force is applied to this embodiment of the multi-axis ankle, the ankle moves in rotation with a fluid motion by pivoting about the pin and simultaneously deforming the elastomeric material. The ankle is also able to move in translation via the inherent tilting ability of the spherical bearing. Since deformation of the elastomeric material in this embodiment is always kept within the elastic limit by means of the dorsi-flexion stop and the limited translational movement of the downwardly-extending projection of the lower leg connection component, breakdown of the elastomeric material is minimized.
Since there is no surface-to-surface sliding motion within any of the aforementioned multi-axis prosthetic ankle embodiments, the material breakdown which might otherwise occur due to friction therebetween is reduced or eliminated.
According to yet a another embodiment of the present invention, a multi-axis prosthetic ankle may simply comprise a bottom component adapted to be connected to a prosthetic foot, a lower leg connection component adapted to be connected to a prosthetic lower leg, an elastomeric material securely connecting the bottom component with the lower leg connection component, and mechanical means for limiting a deformation of the elastic material.